The proposed research will assess the efficacy of an adult smoking cessation program comprising mail and telephone contacts over a 12-month period. This strategy will be compared to 1) a more intensive intervention involving feedback on expired air carbon monoxide (CO) level and thiocyanate monitoring with and without the repeated mail and telephone contacts; and 2) a control comparison condition involving minimal pre-treatment telephone contact and post-treatment assessments. It is hypothesized that, if maintained over a long term, even a minimal intervention program will produce significantly increased smoking cessation rates as compared to the control condition and that this effect can be enhanced by a single face-to-face session. Fifteen hundred men will be randomized into four study groups: a) repeated letter and telephone contact plus biochemical monitoring and feedback; b) repeated letter and telephone contact only; c) biochemical monitoring and feedback only; and d) a repeated-testing control group. Effectiveness of the various interventions will be assessed in terms of 1) self-reported smoking behavior; 2) an objective, multivariate measure of smoking behavior based upon thiocyanate data and carbon monoxide data; and 3) paper and pencil instruments measuring urges to smoke, motivations to quit, and attitudes about smoking. The Public Health perspective on the problem of smoking cessation supports the search for smoking cessation programs which involve minimal contact.